1. Field of the Invention
This invention relates to plastic bags, and more particularly to a pack of T-shirt bags, merchandise bags, trash bags, and the like made preferably of polyolefins, and method of manufacturing same, which can be used with or without bagging racks and which provide for self-opening of the bags as each bag is removed from the pack of bags.
2. Description of the Prior Art
Since the mid-1980's, the use of plastic shopping bags has grown dramatically due to the great advantage plastic bags have over bags made of other materials, such as paper. Plastic bags are typically made of low or high density polyethylene (LDPE and HDPE, respectively), but can be made of any of the polyolefins. LDPE and HDPE bags are stronger, lighter and much more compact than paper bags when stacked, saving valuable storage space at the merchants' checkout counter and storage areas. These attributes also make these bags less expensive to transport. LDPE and HDPE bags can be manufactured and sold much less expensively than competing paper bags, making them the bags of choice for merchants. LDPE and HDPE bags are also environmentally friendly since they require 70 percent less energy to manufacture than competing paper bags and are readily recyclable, and when not recycled, are non-toxic when incinerated or disposed of in landfills.
Many groceries stores and other merchants now use a style of plastic bag to bag groceries called T-shirt bags. T-shirt bags are pleated bags which are closed, by heat sealing, at a bottom edge, and have a pair of integral handles extending upwardly to define an open mouth of the bag therebetween. The handles make the grocery loaded bags easier to carry. Because high density polyethylene (HDPE) has a greater resistance to stretching and deformation, HDPE is generally used for making T-shirt bags, although LDPE and other polyolefins can also be used. T-shirt bags are normally provided in packs of aligned bags and these packs of bags are often used in conjunction with bagging racks.
T-shirt bags are generally manufactured by the following process. A continuous tube of HDPE, or other plastic materials having the desired color, thickness, and diameter is formed on a extruding machine. The continuous plastic tube is then passed over rollers to roll the continuous plastic tube onto a spool. Depending on whether or not the bags to be formed from the continuous tube of HDPE will be printed on one or both sides, the newly formed continuous tube will be subjected to corona surface treatment, wherein the side or sides of the continuous flattened tube of plastic to be later printed will be passed by a high voltage corona discharge electrode. Corona surface treatment affects electrical and chemical changes on the plastic's outer surface to prepare that surface of the bag for printing. As will be discussed below, corona surface treatment, or other known methods to electrically and chemically change the entire outer surface of the continuous plastic tube, has been found useful to insure reliable and consistent self-opening operation of applicant's plastic bag pack system.
After being corona surface treated and rolled, the roll of continuous plastic tube is then pleated, and then a bagging machine heat seams and cuts sections of the pleated tube at top and bottom edges to form closed and flattened pleated bags of a desired length and width, with the pleated sides being at both sides of the flatted pleated bags. Further downstream of the heat seaming and cutting step, the bags are stacked in aligned piles. Thereafter, a hydraulic die or other cutting methods are utilized to remove material at the stacked bags' top portion to form the handles and a central tab portion with a central tab slit for support of the pack of bags on a hook of a bagging neck and a tearing line below the central tab slit. Usually a heat weld is utilized to hold the stack of central tabs together, thus forming a pack of bags. Each handle will comprise four layers of material since they are cut out from the pleated side portions of the bag.
Despite the many advantages HDPE T-shirt bags have over paper bags, unlike thicker and stiffer paper bags with a discreet flat bottom, they are not self-standing. This is due to their relatively thin and flexible material. In grocery stores settings, where quick and easy loading of bags is desirable, T-shirt bags are provided in stacks or packs which are generally supported on a bagging rack as merchandise is loaded into the bags to overcome the lack of self-standing ability.
There are several popular styles of T-shirt bags available in packs of bags and bagging racks for use therewith, some main types of which will be discussed. In one type of pack of T-shirt bags and bagging racks used therewith, the bagging rack has a support base, a wire rear wall with a tab receiving hook, and two wire arms extending forwardly over the base. In the center top portion of the arms, the wire is formed so as to have a section which will spread and hold apart the handles of T-shirt bags engaged therewith to open up the mouth of the T-shirt bag. The pack of T-shirt bags used with these styles of bagging racks consists of a stack of overlapped and aligned bags which have a lower bag portion with two handles extending upwardly at both sides of the mouth of the bag. A central tab portion is provided on the mouth of the bags between the two handles, and the central tab portions of the pack of bags are heat-sealed together. The heat sealed central tabs thus form a stack or book of central tabs and have a central tab slit formed therethrough. The central tab slit is engaged with the tab receiving hook on the rear wall of the bagging rack, and the book of central tabs will remain engaged therewith, even after individual bags are removed. Below the central tab slit a tearing slit is provided which traverses almost the entire distance of the central tabs except for a small distance at both sides of the central tab portion. The tearing slit allows the individual bags to be torn off the pack of bags as they are needed, and looped onto the bagging rack.
A second major type of pack of T-shirt bag, and bagging rack designed to be used therewith, are disclosed in U.S. Pat. No. RE 33,264 to Baxley, et al. Another version of this style of bagging rack is disclosed in U.S. Pat. No. 4,840,336 to Stroh, et al. Both of these bagging racks have a bottom support base and a rear wire wall with a tab receiving hook located thereon. However, to open up each individual bag for loading, instead of looping the handles of the bags over the top of the support arm one at a time, as is done with the first type of pack of bags and rack, these racks have two handle support rods extending forwardly from the rear wire wall of the rack. The pack of T-shirt bags used with these styles of racks are similar to those used with the first type of rack, except that aligned apertures are formed on each handle of the pack of bags, through which pass the handle support rods of the bagging rack.
Both these styles of packs of T-shirt bags suffer from drawbacks; namely, the lack of a self-opening feature. In order to prepare a T-shirt bag for loading with merchandise, only the first layer of the bag material of the top bag, and no other layers must be pulled forward, thereby opening just the top bag. Since the HDPE material is very thin, typically between 1 to 0.5 mil thick (0.001 and 0.0005 inches), it is sometimes difficult for the checkout clerk or box boy to grasp just the top layer of bag material. One can often see a sponge or source of tacky material, such as a glue stick, retained at the top of bagging racks, with which the checkout clerk or box boy can dampen his or her fingers to aid in grasping just the top layer of material of the bag. However, this takes additional time and effort in the bagging process. This cycle will have to be repeated with each successive bag to be loaded.
Several approaches have been taken to overcome these problems. U.S. Pat. No. RE 33,264 to Baxley, et al. discloses a pack of T-shirt bags wherein spots of adhesive are placed between the rear wall of the forwardly lying bags and the front wall of the rearwardly lying bags. The use of these spots is intended to provide for self-opening of the bags as each bag is pulled off the rack. However, the use of spots of adhesive is undesirable from a cost standpoint because of the requirement of an extra manufacturing step of depositing spots of adhesive on the growing stack of closed bags as each subsequent closed bag is stacked thereon, before the die cutting step takes place.
U.S. Pat. No. 5,074,674 to Kuklies, et al. discloses a packs of bags similar to that of Baxley, et al. wherein the front wall of each bag is either relieved or removed in the region of the central tab so as not to be retained by the tab receiving hook on the bagging rack, purportedly allowing the front wall of the bag to be grasped more easily to open the bag. However, this style also requires an extra, and difficult manufacturing step of removing or relieving a portion of only the front wall of each bag. The pack of bags of Kuklies, et al. does not provide for self-opening of the bags.
U.S. Pat. No. 4,877,473 to Snowden, et al. discloses a pack of bags wherein the tearing line has a central arched portion which forms a sub tab. This sub tab can be easily grasped and pulled forward to pull the front wall of each bag to open that particular bag. However, each subsequent bag in the pack of bags must be opened in the same manner.
Despite the attempts to overcome the problems associated with these presently available T-shirt bags, there remains a need for an improved pack of T-shirt bags which can be used with a variety of bagging racks, which can be easily manufactured, and which provides for self-opening of each bag in the pack of bags.